DOCBOOK-APPS: EntityResolver for XSLT processor and catalog files

["M.-A. DARCHE" <ma.darche@free.fr>]

On 20010603 01:20 (Sunday), ben wrote:
> FYI, I've seen the reason why xalan was failing: it is due to the fact that
> xalan creates only a new EntityResolver object, but doesn't provide a catalog
> to the resolver (specific to the catalog entity resolver). I've fixed the
> problem by extending the CatalogEntityResolver class so that by default the
> catalogs are the system ones (xml.catalog.files). If someone is interested, I
> can send the extended class.

Hello,

I've checked the mailing list archive and Ben's statement is may be the
best detailed description of *using Xalan with catalog files support*.
So I think that there is maybe a lack of information on the subject.
Having spend some time to solve this too I think the explanations below
might help others.

I've also augmented Bob Stayton's 
"Using XSL tools to publish DocBook documents".
The modified document is here 
http://ma.darche.free.fr/xml/publishing-augmented.xml
I hope it will make it into the docbook-xsl documentation :-)

As for the EntityResolver wrapper class named here ConfCatEntityResolver,
I do believe that it should be included (or an equivalent) in the java 
catalog classes distribution (in the catalog-apps.jar) because :
- it's not straightforward to use the java catalog classes with an XSL
  processor
- not everyone want to write code before publishing
- it might be a good thing to have the same classname for everyone so
  operating systems distributions can standardize their scripts,
  environment, etc.

Norm, would it be possible to have the java catalog classes hosted on
http://sourceforge.net/projects/docbook/ ?
They will be more widely known and besides that would be more logical
if we are to expect the C or C++ implementation ;-)

Cheers,


=======================================================================

Xalan example
-------------
Here is a simple example of a Unix command line to produce HTML. You'll
need to alter your CLASSPATH environment variable to include the path to
where you put the specified .jar files.

CLASSPATH=xalan.jar:xerces.jar
export CLASSPATH
java \
org.apache.xalan.xslt.Process -html \
-in filename.xml \
-xsl docbook/html/docbook.xsl \
-out output.html


Catalog files support
---------------------
XSLT processors are more efficiently used with catalog files. In order
to benefit from catalog files one can use the Java Catalog classes that
Arbortext released to the XML community.
http://www.arbortext.com/Think_Tank/XML_Resources/Issue_Three/issue_three.html
The example that follows is the Xalan example taken a step further.
In this example catalog should
be replaced by your system catalog file which could be
/usr/lib/sgml/catalog.

CLASSPATH=xalan.jar:xerces.jar:catalog.jar:catalog-apps.jar
export CLASSPATH
java \
-Dxml.catalog.debug=0 \
-Dxml.catalog.override=yes \
-Dxml.catalog.files=catalog \
org.apache.xalan.xslt.Process -html \
-entityresolver ConfCatEntityResolver \
-in filename.xml \
-xsl docbook/html/docbook.xsl \
-out output.html

 Please note that the com.arbortext.catalog.CatalogEntityResolver java
 class cannot be passed directly to Xalan because it doesn't take any
 configuration in charge. So one has to pass a custom made
 EntityResolver to the XSL parser. This is this class listing that
 follows :

ConfCatEntityResolver
---------------------

import java.io.IOException;
import java.net.MalformedURLException;

import org.xml.sax.EntityResolver;

import com.arbortext.catalog.Catalog;
import com.arbortext.catalog.CatalogEntityResolver;

/**
 * ConfCatEntityResolver stands for Configured CatalogEntityResolver
 * and is a wrapper around the CatalogEntityResolver class.<br />
 *
 * This wrapper's purpose is to let any XSLT processor use it
 * as an EntityResolver right out of the box, without the parser needing
 * to configure the specific CatalogEntityResolver.
 */
public class ConfCatEntityResolver extends CatalogEntityResolver {

    public ConfCatEntityResolver() {
	super();
	Catalog catalog = new Catalog();
	try {
	    catalog.loadSystemCatalogs();
	    this.setCatalog(catalog);
	} catch
	(MalformedURLException
	 muex) {
	    muex.printStackTrace();
	} catch
	(IOException
	 ioex) {
	    ioex.printStackTrace();
	}

    }

}


-- 
Marc-Aurčle DARCHE  <http://ma.darche.free.fr>
AFUL <http://www.aful.org>
Association Francophone des Utilisateurs de Linux/Logiciels Libres
French speaking Linux and Free Software Users' Association